Light-sensitive material containing silver halide, reducing agent and polymerizable compound

ABSTRACT

A light-sensitive material comprising a light-sensitive layer containing silver halide, a reducing agent, a polymerizable compound and a leuco dye provided on a support, characterized in that the leuco dye is a compound having the following formula (I): ##STR1## in which A is --O--or ##STR2## and R is a substituent having a positive substituent constant (σ); each of R 1  and R 2  is an alkyl group, a cycloalkyl group or an aralkyl group; each of R 3 , R 4  and R 5  is an alkyl group, an alkoxy group, a cycloalkyl group, an aralkyl group or an aryloxy group; each of k, l and n is 1 or 2; and m is 0, 1 or 2.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a light-sensitive material comprising alight-sensitive layer containing silver halide, a reducing agent, apolymerizable compound and a leuco dye (serving as color image formingsubstance) provided on a support.

2. Description of Prior Art

Light-sensitive materials comprising a light-sensitive layer containingsilver halide, a reducing agent and a polymerizable compound provided ona support can be used in an image forming method in which a latent imageof silver halide is formed, and then the polymerizable compound ispolymerized to form the corresponding image.

Examples of said image forming methods are described in Japanese PatentPublication Nos. 45(1970)-11149 (corresponding to U.S. Pat. No.3,697,275), 47(1972)-20741 (corresponding to U.S. Pat. No. 3,687,667)and 49(1974)-10697, and Japanese Patent Provisional Publication Nos.57(1982)-138632, 57(1982)-142638, 57(1982)-176033, 57(1982)-211146(corresponding to U.S. Pat. No. 4,557,997), 58(1983)-107529(corresponding to U.S. Pat. No. 4,560,637), 58(1983)-121031(corresponding to U.S. Pat. No. 4,547,450) and 58(1983)-169143. In theseimage forming methods, when the exposed silver halide is developed usinga developing solution, the polymerizable compound is induced topolymerize in the presence of a reducing agent (which is oxidized) toform a polymer image. Thus, these methods need a wet development processemploying a developing solution. Therefore the process takes arelatively long time for the operation.

An improved image forming method employing a dry process is described inJapanese Patent Provisional Publication Nos. 61(1986)-69062 and61(1986)-73145 (the contents of both publications are described in U.S.Pat. No. 4,629,676 and European Patent Provisional Publication No.0174634A2). In this image forming method, a recording material (i.e.,light-sensitive material) comprising a light-sensitive layer containinga light-sensitive silver salt (i.e., silver halide), a reducing agent, across-linkable compound (i.e., polymerizable compound) and a binderprovided on a support is imagewise exposed to form a latent image, andthen the material is heated to polymerize within the area where thelatent image of the silver halide has been formed. The above methodemploying the dry process and the light-sensitive material employablefor such method are also described in Japanese Patent ProvisionalPublication Nos. 61(1986)-183640, 61(1986)-188535 and 61(1986)-228441.

The above-mentioned image forming methods are based on the principle inwhich the polymerizable compound is polymerized within the area where alatent image of the silver halide has been formed.

Japanese Patent Provisional Publication No. 61(1986)-73145(corresponding to U.S. Pat. No. 4,629,676 and European PatentProvisional Publication No. 0174634A2) describes an embodiment of theimage-forming methods, which employs a light-sensitive materialcomprising a light-sensitive layer containing silver halide, a reducingagent, a polymerizable compound and a color image forming substanceprovided on a support. The image-forming method comprises: imagewiseexposing the light-sensitive material to form a latent image of silverhalide; and simultaneously or thereafter developing the light-sensitivematerial to polymerize the polymerizable compound, and thereby fixingthe color image forming substance on the support within the area wherethe polymerizable compound has been polymerized.

An example of the color image forming substance employable for the abovementioned image-forming method is a leuco dye, which is also called aredox dye. The leuco dye can develop to give a color in contact with anacid color developer. These leuco dyes have been mainly used in apressure sensitive paper.

SUMMARY OF THE INVENTION

The present inventors have found that the leuco dyes in the pressuresensitive paper do not always satisfy the requirement in thelight-sensitive material. In particular, most of the leuco dyes whichdevelop to give a yellow color do not satisfy the requirement withrespect to the developability and the durability of the obtained colorimage.

Therefore, an object of the present invention is to provide alight-sensitive material which gives an improved color image having aclear yellow color.

Another object of the invention is to provide a light-sensitive materialwhich gives an image improved in the fastness to light.

There is provided by the present invention a light-sensitive materialcomprising a light-sensitive layer contaiing silver halide, a reducingagent, a polymerizable compound and a leuco dye provided on a support,characterized in that the leuco dye is a compound having the followingformula (I): ##STR3## in which A is --O-- or ##STR4## and R is asubstituent having a positive substituent constant (σ); each of R¹ andR² independently is a group selected from the group consisting of analkyl group, a cycloalkyl group and an aralkyl group; each of R³, R⁴ andR⁵ independently is a group selected from the group consisting of analkyl group, an alkoxy group, a cycloalkyl group, an aralkyl group andan aryloxy group; each of k, l and n independently is 1 or 2; and m is0, 1 or 2.

The light-sensitive material of the invention can be advantageously usedin a process which comprises:

imagewise exposing the light-sensitive material to form a latent imageof the silver halide;

simultaneously or thereafter developing the light-sensitive material topolymerize the polymerizable compound within the area where the latentimage of the silver halide has been formed (or the area where the latentimage of the silver halide has not been formed), and thereby fixing theleuco dye on the support within the area; and

pressing the light-sensitive material on an image-receiving materialcomprising an image-receiving layer containing an acid color developerprovided on a support to transfer the unfixed leuco dye to theimage-receiving material, and thereby the leuco dye reacting with theacid color developer to form a color image on the image-receivingmaterial.

The light-sensitive material of the invention is characterised inemploying the specific leuco dye of the formula (I) as a color imageforming substance.

The light-sensitive material employing the leuco dye of the formula (I)as a yellow color image forming substance gives a clear image having ahigh maximum density and a low minimum density, that is an image havinga high contrast.

Therefore, the light-sensitive material of the present invention cangive a very clear image.

Some leuco dyes having the formula (I) are known and proposed for use ina pressure sensitive paper, which is described in Japanese PatentPublication No. 50(1975)-24646.

Further, the present inventors have found that the new leuco dyes havingthe following formula (II) can be more advantageously used in thelight-sensitive material. ##STR5## in which R¹ and R² are the samegroups selected from the group consisting of an alkyl group and acycloalkyl group; R³ and R⁴ are the same groups selected from the groupconsisting of an alkyl group, a cycloalkyl group and an alkoxy group;and the sum of carbon atoms contained in R¹ and R³ is not less than 5.

DETAILED DESCRIPTION OF THE INVENTION

The leuco dyes employed in the present invention has the followingformula (I). ##STR6##

In the formula (I), A is --O-- or ##STR7## The substituent representedby R is a group having a positive substituent constant in terms of σ(σ>0). The term "substituent constant (σ)" means a numerical valuededuced from Hammett's rule. The value (σ) is inherent in thesubstituent group and is calculated from the dissociation reaction of abenzoic acid derivative in water at 25° C. The "R" is a substituentgroup having a positive σ value (electron attractive group).Accordingly, any of electron attractive groups may be used as thesubstituent "R" in the present invention. For example, such groupshaving a positive σ value can be chosen from those set forth in theliterature "Structure-Activity Correlation of Medicines", pp. 96-103,(1979) (written in Japanese) published by Nankodo, Japan, edited byStructure-Activity Correlation Conversazione (Representative: ToshioFujita).

Among them, the substituent groups having a substituent constant σ offrom +0.23 to +0.78 are preferred, and particularly preferredsubstituents are Cl, CN, SO₂ CH₃ and NO₂ from the viewpoint of ease ofproduction.

In the formula (I), each of R¹ and R² independently is a group selectedfrom the group consisting of an alkyl group, a cycloalkyl group and anaralkyl group, and each of R³, R⁴ and R⁵ independently is a groupselected from the group consisting of an alkyl group, an alkoxy group, acycloalkyl group, an aralkyl group and an aryloxy group.

The alkyl group represented by R¹, R², R³, R⁴ and R⁵ preferably has 1 to22 carbon atoms, more preferably 1 to 12 carbon atoms, may be a straightchain or branched chain alkyl and may be substituted with cyano, analkoxy group and hydroxyl.

Examples of the cycloalkyl groups represented by R¹, R², R³, R⁴ and R⁵include cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl.

Examples of the aralkyl groups represented by R¹, R², R³, R⁴ and R⁵include benzyl and phenethyl. The phenyl moiety of the aralkyl group maybe substituted with a substituent group having a substituent constant offrom -0.27 to 0.78. The substituent groups having a value within therange specified above include electron donative groups (σ<0) in additionto the electron attractive groups such as Cl. Examples of such electrondonative groups include an alkyl group such as methyl.

The alkyl moiety of the alkoxy group represented by R³, R⁴ and R⁵preferably has 1 to 16 carbon atoms, more preferably 1 to 8 carbonatoms. The alkyl moiety may be substituted with a substituent group suchas cyano, alkoxy and hydroxyl groups.

The aryl moiety of the aryloxy group represented by R³, R⁴ and R⁵preferably is phenyl group and may be substituted with a substituentgroup having a substituent constant σ of from -0.27 to +0.78 asdescribed above.

In the formula (I), k, l and n are each 1 or 2, and m is 0 to 2.

In the preferred embodiment, the leuco dyes of the invention arecompounds having the following formula (II). ##STR8## in which R¹ and R²are the same groups selected from the group consisting of an alkyl groupand a cycloalkyl group; R³ and R⁴ are the same groups selected from thegroup consisting of an alkyl group, a cycloalkyl group and an alkoxygroup; and the sum of carbon atoms contained in R¹ and R³ is not lessthan 5.

In the formula (II), the alkyl group represented by R¹, R², R³ and R⁴preferably has 1 to 22 carbon atoms, more preferably 1 to 12 carbonatoms, may be straight chain or branched chain alkyl and may besubstituted with a substituent group such as cyano, an alkoxy group andhydroxyl.

Examples of the cycloalkyl groups represented by R¹, R², R³ and R⁴include cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl.

Examples of the aralkyl groups represented by R³ and R⁴ include benzyland phenethyl. The phenethyl may be substituted with a substituent grouphaving a substituent constant σ of from -0.27 to +0.78 as describedabove.

In the formula (II), R¹ and R² are the same group, R³ and R⁴ are thesame group, and the sum of carbon atoms contained in R¹ and R³ (or R¹and R⁴, R² and R³, or R² and R⁴) is 5 or greater.

Examples of the leuco dyes which are preferably used in the inventionare described hereinafter. ##STR9##

The leuco dyes used in the present invention can be easily synthesizedby the following procedure.

SYNTHESIS EXAMPLE 1 Synthesis of lueco dye (1)

In a three-neckd flask were placed 75 g of 4-n-hexylresorcinol, 28.6 gof phthalic anhydride and 26.4 g of zinc chloride, and the mixture wasstirred at 130° C. for 4 hours. To the reaction mixture were added waterand ethyl acetate to make extraction. The resulting oily layer wasconcentrated, and crystals were precipitated by addition of n-hexane andrecovered by filtration. The yield was 52.6 g, m.p. 201°-203° C.

In a 200 ml three-necked flask were placed 10 g of the fluoran compoundobtained above, 5.6 g of sodium hydroxide and 100 ml of water. To themixture was portionwise added 26 g of methyl p-toluenesulfonate at atemperature of 50° to 60° C. The mixture was then left to stand at roomtemperature, and the precipitated crystals were recovered by filtrationand purified by means of column chromatograph (solvent: n-hexane/ethylacetate=10/1). The yield was 2.1 g, m.p. 91°-92° C.

The other leuco dyes can also be prepared by procedures similar to theprocedure of Synthesis Example 1.

These leuco dyes can be uses singly or in combination.

When the leuco dye (yellow) of the present invention is used togetherwith two or more known leuco dyes having different hue in combination,they can be used in combination with at least three silver halideemulsions (described hereinafter) having light sensitivity in differentspectral regions so as to make them to correspond to each emulsion,whereby a full color image can be formed.

The leuco dye in the light-sensitive layer of the light-sensitivematerial is preferably used in an amount of from 0.5 to 50 weight %based on the amount of the polymerizable compound, and more preferablyfrom 2 to 20 weight %.

In the light-sensitive material of the invention, the leuco dye isbrought into contact with an acid developer in the formation of thecolor image.

The reaction of the color formation can be much accelerated by heating.Therefore, the leuco dyes preferably react with the developer under aheating condition.

Heating temperatures for the reaction usually ranges from 50° C. to 200°C., and preferably from 50° C. to 150° C. The heating time is usuallyfrom 1 second to 1 minute, and preferably from 1 second to 10 seconds.

In the image formation employing the light-sensitive material of theinvention, the color image is preferably formed on an image-receivingmaterial to improve the sensitivity of the light-sensitive material andthe sharpness of the obtained image. In this case, the acid colordeveloper is previously contained in an image-receiving layer of theimage-receiving material.

Alternatively, the acid color developer can be contained in thelight-sensitive material of the invention as one of the optionalcomponents of the light-sensitive layer. Where the leuco dyes and thepolymerizable compound are contained in a microcapsule, and the acidcolor developer is arranged outside of the microcapsule in thelight-sensitive layer, a color image can be formed on thelight-sensitive layer. In this case, the acid color developer can becontained in a different microcapsule from that containing the leucodyes.

Examples of the acid color developers include an acid clay developer(e.g., China clay), phenol-formaldehyde resins (e.g.,p-phenylphenol-formaldehyde resin), metal salts of salicylic acids(e.g., zinc 3,5-di-α-methylbenzyl salicylate), phenol-salicylicacid-formaldehyde resin (e.g., p-octylphenol-zincsalicylate-formaldehyde resin), zinc rhodanide and zinc xanthate.

Among them, the metal salts of the salicylic acids are preferred, andzinc salicylates are most preferred. It has been found that the reactionof the color formation of the leuco compound proceeds rapidly andeffectively in the presence of zinc salicylates. The metal salts of thesalicylates are described in more detail in Japanese Patent PublicationNo. 52(1977)-1327. The oil-soluble color developers containing zincsalicylates are described in U.S. Pat. Nos. 3,864,146 and 4,046,941.

The acid color developer is preferably used in an amount of from 50 to1,000 weight % based on the amount of the leuco dyes, and morepreferably from 100 to 1,000 weight %.

The silver halide, the reducing agent, the polymerizable compound andthe support which constitute the light-sensitive material of theinvention are described below. Thus composed material is referredhereinafter to as "light-sensitive material".

There is no specific limitation with respect to silver halide containedin the light-sensitive layer of the light-sensitive material. Examplesof the silver halides include as silver chloride, silver bromide, silveriodide, silver chlorobromide, silver chloroiodide, silver iodobromide,and silver chloroiodobromide in the form of grains.

The halogen composition of individual grains may be homogeneous orheterogeneous. The heterogeneous grains having a multilayered structurein which the halogen composition varies from the core to the outer shell(see Japanese Patent Provisional Publication Nos. 57(1982)-154232,58(1983)-108533, 59(1984)-48755 and 59(1984)-52237, U.S. Pat. No.4,433,048, and European Pat. No. 100,984) can be employed. A silverhalide grain having a core/shell structure in which the silver iodidecontent in the shell is higher than that in the core can be alsoemployed.

There is no specific limitation on the crystal habit of silver halidegrains. For example, a tubular grain having an aspect ratio of not lessthan 3 can be used.

Two or more kinds of silver halide grains which differ in halogencomposition, crystal habit, grain size, and/or other features from eachother can be used in combination.

There is no specific limitation on grain size distribution of silverhalide grains. For example, the silver halide grains having such a grainsize distribution that the coefficient of the variation is not more than20% can be employed.

The silver halide grains ordinarily have a mean size of 0.001 to 5 μm,preferably 0.001 to 2 μm.

The total silver content (including silver halide and an organic silversalt which is one of optional components) in the light-sensitive layerpreferably is in the range of from 0.1 mg/m² to 10 g/m². The silvercontent of the silver halide in the light-sensitive layer preferably isnot more than 0.1 g/m², more preferably in the range of from 1 mg to 90mg/m².

The reducing agent employed in the light-sensitive material has afunction of reducing the silver halide and/or a function of acceleratingor restraining a polymerization of the polymerizable compound. Examplesof the reducing agents having these functions include various compounds,such as hydroquinones, catechols, p-aminophenols, p-phenylenediamines,3-pyrazolidones, 3-aminopyrazoles, 4-amino-5-pyrazolones,5-aminouracils, 4,5-dihydroxy-6-aminopyrimidines, reductones,aminoreductones, o- or p-sulfonamidophenols, o- orp-sulfonamidonaphthols, 2-sulfonamidoindanones,4-sulfonamido-5-pyrazolones, 3-sulfonamidoindoles,sulfonamidopyrazolobenzimidazoles, sulfonamidopyrazolotriazoles,α-sulfonamidoketones, hydrazines, etc. Depending on the nature or amountof the reducing agent, the polymerizable compound within either the areawhere a latent image of the silver halide has been formed or the areawhere a latent image of the silver halide has not been formed can bepolymerized. In the developing system in which the polymerizablecompound within the area where the latent image has not been formed ispolymerized, 1-phenyl-3-pyrazolidone is preferably employed as thereducing agent.

The light-sensitive materials employing the reducing agent having thesefunctions (including compounds referred to as developing agent,hydrazine derivative or precursor of reducing agent) are described inJapanese Patent Provisional Publication Nos. 61(1986)-183640,61(1986)-188535 and 61(1986)-228441. These reducing agents are alsodescribed in T. James, "The Theory of the Photographic Process", 4thedition, pp. 291-334 (1977), Research Disclosure No. 17029, pp. 9-15(June 1978), and Research Disclosur No. 17643, pp. 22-31 (December1978). The reducing agents described in the these publications can beemployed in the light-sensitive material of the present invention. Thus,"the reducing agent(s)" in the present specification means to includeall of the reducing agents described in the above mentioned publicationsand applications.

These reducing agents can be used singly or in combination. In the casethat two or more reducing agents are used in combination, certaininteractions between these reducing agents may be expected. One of theinteractions is for acceleration of reduction of silver halide (and/oran organic silver salt) through so-called super-additivity. Otherinteraction is for a chain reaction in which an oxidized state of onereducing agent formed by a reduction of silver halide (and/or an organicsilver salt) induces or inhibits the polymerization of the polymerizablecompound via oxidation-reduction reaction with other reducing agent.Both interactions may occur simultaneously. Thus, it is difficult todetermine which of the interactions has occurred in practical use.

Examples of these reducing agents include pentadecylhydroquinone,5-t-butylcatechol, p-(N,N-diethylamino)phenol,1-phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidone,1-phenyl-4-methyl-4-heptadecylcarbonyloxymethyl-3-pyrazolidone,2-phenylsulfonylamino-4-hexadecyloxy-5-t-octylphenol,2-phenylsulfonylamino-4-t-butyl-5-hexadecyloxyphenol,2-(N-butylcarbamoyl)-4-phenylsulfonylaminonaphtol,2-(N-methyl-N-octadecylcarbamoyl)-4-sulfonylaminonaphthol,1-acetyl-2-phenylhydrazine, 1-acetyl-2-(p- or o-aminophenyl)hydrazine,1-formyl-2-(p- or o-aminophenyl)hydrazine, 1-acetyl-2-(p- oro-methoxyphenyl)hydrazine, 1-lauroyl-2-(p- or o-aminophenyl)hydrazine,1-trityl-2-(2,6-dichloro-4-cyanophenyl)hydrazine,1-trityl-2-phenylhydrazine, 1-phenyl-2-(2,4,6-trichlorophenyl)hydrazine,1-{2-(2,5-di-tert-pentylphenoxy)butyloyl}-2-(p- oro-aminophenyl)hydrazine, 1-{2-(2,5-di-t-pentylphenoxy)butyloyl}-2-(p- oro-aminophenyl)hydrazine pentadecylfluorocaprylate salt, 3-indazolinone,1-(3,5-dichlorobenzoyl)-2-phenylhydrazine,1-trityl-2-[{(2-N-butyl-N-octylsulfamoyl)-4-methanesulfonyl}phenyl]hydrazine,1-{4-(2,5-di-tert-pentylphenoxy)butyloyl}-2-(p- oro-methoxyphenyl)hydrazine,1-(methoxycarbonylbenzohydryl)-2-phenylhydrazine,1-formyl-2-[4-{2-(2,4-di-tert-pentylphenoxy)butylamide}phenyl]hydrazine,1-acetyl-2-[4-{2-(2,4-di-tert-pentylphenoxy)butylamido}phenyl]hydrazine,1-trityl-2-[{2,6-dichloro-4-(N,N-di-2-ethylhexyl)carbamoyl]phenyl]hydrazine,1-(methoxycarbonylbenzohydryl)-2-(2,4-dichlorophenyl)hydrazine,1-trityl-2-[{2-(N-ethyl-N-octylsulfamoyl)-4-methanesulfonyl}phenyl]hydrazine,1-benzoyl-2-tritylhydrazine, 1-(4-butoxybenzoyl)-2-tritylhydrazine,1-(2,4-dimethoxybenzoyl)-2-tritylhydrazine,1-(4-dibutylcarbamoylbenzoyl)-2-tritylhydrazine and1-(1-naphthoyl)-2-tritylhydrazine.

The amount of the reducing agent in the light-sensitive layer preferablyranges from 0.1 to 1,500 mole % based on the amount of silver (containedin the above-mentioned silver halide and an organic silver salt).

There is no specific limitation with respect to the polymerizablecompound, and any known polymerizable compounds including monomers,oligomers and polymers can be contained in the light-sensitive layer. Inthe case that heat development (i.e., thermal development) is utilizedfor developing the light-sensitive material, the polymerizable compoundshaving a relatively higher boiling. point (e.g., 80° C. or higher) thatare hardly evaporated upon heating are preferably employed. In the casethat the light-sensitive layer contains a color image forming substance,the polymerizable compounds are preferably cross-linkable compoundshaving plural polymerizable groups in the molecule, because suchcross-linkable compounds favorably serve for fixing the leuco dyes inthe course of polymerization hardening of the polymerizable compounds.

The polymerizable compound employable for the light-sensitive materialare described in the above-mentioned and later-mentioned publicationsconcerning the light-sensitive material.

Preferred polymerizable compounds employable for the light-sensitivematerial are compounds which are polymerizable through addition reactionor ring-opening reaction. Preferred examples of the compounds beingpolymerizable through addition reaction include compounds having anethylenic unsaturated group. Preferred examples of the compounds beingpolymerizable through ring-opening reaction include the compounds havingan epoxy group. Among them, the compounds having an ethylenicunsaturated group are preferred.

Examples of compounds having an ethylenic unsaturated group includeacrylic acid, salts of acrylic acid, acrylic esters, acrylamides,methacrylic acid, salts of methacrylic acid, methacrylic esters,methacrylamide, maleic anhydride, maleic esters, itaconic esters,styrene, styrene derivatives, vinyl ethers, vinyl esters, N-vinylheterocyclic compounds, allyl ethers, allyl esters, and compoundscarrying a group or groups corresponding to one or more of thesecompounds.

Concrete examples of the acrylic esters include n-butyl acrylate,cyclohexyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, furfurylacrylate, ethoxyethoxy acrylate, dicyclohexyloxyethyl acrylate,nonylphenyloxyethyl acrylate, hexanediol diacrylate, butanedioldiacrylate, neopentylglycol diacrylate, trimethylolpropane triacrylate,pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate,diacrylate of polyoxyethylenated bisphenol A, polyacrylate ofhydroxypolyether, polyester acrylate, and polyurethane acrylate.

Concrete examples of the methacrylic esters include methyl methacrylate,butyl methacrylate, ethylene glycol dimethacrylate, butanedioldimethacrylate, neopentylglycol dimethacrylate, trimethylolpropanetrimethacrylate, pentaerythritol trimethacrylate, pentaerythritoltetramethacrylate, and dimethacrylate of polyoxyalkylenated bisphenol A.

The polymerizable compounds can be used singly or in combination of twoor more compounds. For example, a mixture of two or more polymerizablecompounds can be employed. Further, compounds formed by bonding apolymerizable group such as a vinyl group or a vinylidene group to areducing agent or a color image forming substance are also employed asthe polymerizable compounds. The light-sensitive materials employingthese compounds which show functions as both the reducing agent and thepolymerizable compound, or of the color image forming substance and thepolymerizable compound are included in embodiments of the invention.

The amount of the polymerizable compound for incorporation into thelight-sensitive layer preferably ranges from 5 to 1.2×10⁵ times (byweight) as much as the amount of silver halide, more preferably from 10to 1×10⁴ times as much as the silver halide.

The light-sensitive material can be prepared by arranging alight-sensitive layer containing the above-mentioned components on asupport. There is no limitation with respect to the support. In the casethat heat development is utilized in the use of the light-sensitivematerial, material of the support preferably is resistant to heat givenin the processing stage. Examples of the material employable for thepreparation of the support include glass, paper, fine paper, coat paper,synthetic paper, metals and analogues thereof, polyester, acetylcellulose, cellulose ester, polyvinyl acetal, polystyrene,polycarbonate, polyethylene terephthalate, and paper laminated withresin or polymer (e.g., polyethylene). In the case that a porousmaterial, such as paper is employed as the support, the porous supportpreferably has such a surface characteristic that a filtered maximumwaviness of not less than 4 μm is observed in not more than 20 positionsamong 100 positions which are determined at random on a filteredwaviness curve obtained according to JIS-B-0610.

Various embodiments of the light-sensitive materials, optionalcomponents which may be contained in the light-sensitive layer, andauxiliary layers which may be optionally arranged on the light-sensitivematerials are described below.

The polymerizable compound is preferably dispersed in the form of oildroplets in the light-sensitive layer. Other components in thelight-sensitive layer, such as silver halide, the reducing agent, theleuco dyes may be also contained in the oil droplets.

The oil droplets of the polymerizable compound are preferably preparedin the form of microcapsules. There is no specific limitation onpreparation of the microcapsules.

There is also no specific limitation on shell material of themicrocapsule, and various known materials such as polymers which areemployed in the conventional microcapsules can be employed as the shellmaterial. Examples of the shell material include polyamide resin and/orpolyester resin, polyurea resin and/or polyurethane resin, aminoaldehyderesin, gelatin, epoxy resin, a complex resin containing polyamide resinand polyurea resin, a complex resin containing polyurethane resin andpolyester resin.

The mean size of the microcapsule preferably ranges from 0.5 to 50 μm,more preferably 1 to 25 μm, most preferably 3 to 20 μm. In the case thatsilver halide grains are contained in the microcapsule, the mean grainsized of the silver halide grains preferably is not more than the 5thpart of the mean size of the microcapsules, more preferably is not morethan the 10th part. It is observed that when the mean sized of themicrocapsules is not less than 5 times are much as the mean grain sizeof silver halide grains, even and uniform image can be obtained.

In the case that silver halide grains are contained in the microcapsule,the silver halide grains are preferably arranged in the shell materialof the microcapsules.

Further, two or more kinds of the microcapsules differing from eachother with respect to at least one of the silver halide, thepolymerizable compound and the leuco dyes can be employed. Furthermore,three or more kinds of the microcapsules differing from each other withrespect to the leuco dyes including the above-mentioned leuco dye(yellow) is preferably employed to form a full color image.

The light-sensitive layer can further contain optional components suchas other color image forming substances than the leuco dyes, sensitizingdyes, organic silver salts, various kinds of image formationaccelerators, thermal polymerization inhibitors, thermal polymerizationinitiators, development stopping agents, fluorescent brightening agents,discoloration inhibitors, antihalation dyes or pigments, antiirradiationdyes or pigments, matting agents, antismudging agents, plasticizers,water releasers, binders, photo polymerization initiators and solventsof the polymerizable compound.

The light-sensitive material of the invention utilizes the leuco dyes asa color image forming substance. The light-sensitive material canfurther contain other color image forming substance than the lueco dyes.There is no specific limitation with respect to other color imageforming substance, and various kinds of substances can be employed.Thus, examples of the color image forming substance include both coloredsubstance (i.e., dyes and pigments) and non-colored or almostnon-colored substance (i.e., color former or dye- or pigment-precursor)which develops to give a color under application of external energy(e.g., heating, pressing, light irradiation, etc.) or by contact withother components (i.e., developer). The light-sensitive material usingthe color image forming substance is described in Japanese PatentProvisional Publication No. 61(1986)-73145 (corresponding to U.S. Pat.No. 4,629,676 and European Patent Provisional Publication No.0174634A2).

There is no specific limitation with respect to the sensitizing dyes,and known sensitizing dyes used in the conventional art of photographymay be employed in the light-sensitive material. Examples of thesensitizing dyes include methine dyes, cyanine dyes, merocyanine dyes,complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes,hemicyanine dyes, styryl dyes, and hemioxonol dyes. These sensitizingdyes can be used singly or in combination. Combinations of sensitizingdyes are often used for the purpose of supersensitization. In additionto the sensitizing dyes, a substance which does not per se exhibitspectral sensitization effect or does not substantially absorb visiblelight but shows supersensitizing activity can be used. The amount of thesensitizing dye to be added generally ranges from about 10⁻⁸ to about10⁻² mol per 1 mol of silver halide. The sensitizing dye is preferablyadded during the stage of the preparation of the silver halide emulsion(simultaneously with or after the grain formation).

When the heat development is employed in the use of the light-sensitivematerial, an organic silver salt is preferably contained in thelight-sensitive material. It can be assumed that the organic silver salttakes part in a redox reaction using a silver halide latent image as acatalyst when heated to a temperature of 80° C. or higher. In such case,the silver halide and the organic silver salt preferably are located incontact with each other or close together. Examples of organic compoundsemployable for forming such organic silver salt include aliphatic oraromatic carboxylic acids, thiocarbonyl group-containing compoundshaving a mercapto group or an α-hydrogen atom, imino group-containingcompounds, and the like. Among them, benzotriazoles are most preferable.The organic silver salt is preferably used in an amount of from 0.01 to10 mol., and preferably from 0.01 to 1 mol., per 1 mol. of thelight-sensitive silver halide. Instead of the organic silver salt, anorganic compound (e.g., benzotriazole) which can form an organic silversalt in combination with an inorganic silver salt can be added to thelight-sensitive layer to obtain the same effect.

Various image formation accelerators are employable in thelight-sensitive material. The image formation accelerators have afunction to accelerate the oxidation-reduction reaction between a silverhalide (and/or an organic silver salt) and a reducing agent, a functionto accelerate emigration of an image forming substance from alight-sensitive layer to an image-receiving material or animage-receiving layer, or a similar function. The image formationaccelerators can be classified into inoragnic bases, organic bases, baseprecursors, oils, surface active agents, compounds functioning as anantifogging agent and/or a development accelerator, hot-melt solvents,antioxidants and the like. These groups, however, generally have certaincombined functions, i.e., two or more of the above-mentioned effects.Thus, the above classification is for the sake of convenience, and onecompound often has a plurality of functions combined.

Various examples of these image formation accelerators are shown below.

Preferred examples of the inorganic bases include hydroxides of alkalimetals or alkaline earth metals; secondary or tertiary phosphates,borates, carbonates, quinolinates and metaborates of alkali metals oralkaline earth metals; a combination of zinc hydroxide or zinc oxide anda chelating agent (e.g., sodium picolinate); ammonium hydroxide;hyrdoxides of quaternary alkylammoniums; and hydroxides of other metals.Preferred examples of the organic bases include aliphatic amines (e.g.,trialkylamines, hydroxylamines and aliphatic polyamines); aromaticamines (e.g., N-alkyl-substituted aromatic amines,N-hydroxylalkyl-substituted aromatic amines andbis[p-(dialkylamino)phenyl]-methanes), heterocyclic amines, amidines,cyclic amidines, guanidines, and cyclic guanidines. Of these bases,those having a pKa of 7 or more are preferred.

The base precursors preferably are those capable of releasing bases uponreaction by heating, such as salts between bases and organic acidscapable of decarboxylation by heating, compounds capable of releasingamines through intramolecular nucleophilic substitution, Lossenrearrangement, or Beckmann rearrangement, and the like; and thosecapable of releasing bases by electrolysis. Preferred examples of thebase precursors include guanidine trichloroacetate, piperidinetrichloroacetate, morpholine trichloroacetate, p-toluidinetrichloroacetate, 2-picoline trichloroacetate, guanidinephenylsulfonylacetate, guanidine 4-chlorophenylsulfonylacetate,guanidine 4-methyl-sulfonylphenylsulfonylacetate, and4-acetylaminomethyl propionate.

These bases or base precursors are preferably used in an amount of notmore than 100% by weight, and more preferably from 0.1 to 40% by weight,based on the total solid content of the light-sensitive layer. Thesebases or base precursors can be used singly or in combination.

In the light-sensitive material, the silver halide, the reducing agent,the polymerizable compound and the leuco dyes are preferably containedin a microcapsule and the base or base precursor is prefarably arrangedoutside of the microcapsule in the light-sensitive layer. Further, thebase or base precursor can be contained in a different microcapsule fromthat containing the polymerizable compound. The base or base precursorcan be contained in the microcapsule under condition that the base orbase precursor is dissolved or dispersed in an aqueous solution of awater retention agent, orr under condition that the base or baseprecursor is adsorbed on solid particles. Furthermore, the base or baseprecursor can be contained in a layer different from the light-sensitivelayer.

Examples of the oils employable in the invention include high-boilingorganic solvents which are used as solvents in emulsifying and dispesinghydrophobic compounds.

Examples of the surface active agents employable in the inventioninclude pyridinium salts, ammonium salts and phosphonium salts asdescribed in Japanese Patent Provisional Publication No. 59(1984)-74547;polyalkylene oxides as described in Japanese Patent ProvisionalPublication No. 59(1984)-57231.

The compounds functioning as an antifogging agent and/or a developmentaccelerator are used to give a clear image having a high maximum densityand a low minimum density (an image having high contrast). Examples ofthe compounds include a 5- or 6-membered nitrogen containingheterocyclic compound (e.g., a cyclic amide compound), a thioureaderivative, a thioether compound, a polyethylene glycol derivative, athiol derivative, an acetylene compound and a sulfonamide derivative.

The hot-melt solvents preferably are compounds which may be used assolvent of the reducing agent or those which have high dielectricconstant and can accelerate physical development of silver salts.Examples of the hot-melt solvents include polyethylene glycols,derivatives of polyethylene oxides (e.g., oleate ester), beeswax,monostearin and high dielectric constant compounds having --SO₂ --and/or --CO-- group described in U.S. Pat. No. 3,347,675; polarcompounds described in U.S. Pat. No. 3,667,959; and 1,10-decanediol,methyl anisate and biphenyl suberate described in Research Disclosure26-28 (December 1976). The light-sensitive material employing thehot-melt solvents is described in Japanese Patent Application No.60(1985)-227527. The hot-melt solvent is preferably used in an amount offrom 0.05 to 50% by weight, and more preferably from 1 to 20% by weight,based on the total solid content of the light-sensitive layer.

The antioxidants can be used to eliminate the influence of the oxygenwhich has an effect of inhibiting polymerization in the developmentprocess. Example of the antioxidants is a compound having two or moremercapto groups.

The thermal polymerization initiators employable in the light-sensitivematerial preferably are compounds that are decomposed under heating togenerate a polymerization initiating species, particularly a radical,and those commonly employed as initiators of radical polymerization. Thethermal polymerization initiators are described in "AdditionPolymerization and Ring Opening Polymerization", pp. 6-18, edited by theEditorial Committee of High Polymer Experimental Study of the HighPolymer Institute, published by Kyoritsu Shuppan (1983). Examples of thethermal polymerization initiators include azo compounds, e.g.,azobisisobutyronitrile, 1,1'-azobis(1-cyclohexanecarbonitrile), dimethyl2,2'-azobisisobutyrate, 2,2'-azobis(2-methylbutyronitrile), andazobisdimethylvaleronitrile; organic peroxides, e.g., benzoyl peroxide,di-tert-butyl peroxide, dicumyl peroxide, tert-butyl hydroperoxide, andcumene hydroperoxide; inorganic peroxides, e.g., hydrogen peroxide,potassium persulfate, and ammonium persulfate; and sodiump-toluenesulfinate. The thermal polymerization initiators are preferablyused in an amount of from 0.1 to 120% by weight, and more preferablyfrom 1 to 10% by weight, based on amount of the polymerizable compound.In a system in which the polymerizable compound within the area wherethe latent image has not been formed is polymerized, the thermalpolymerization initiators are preferably incorporated into thelight-sensitive layer. The light-sensitive material employing thethermal polymerization initiators is described in Japanese PatentProvisional Publication No. 61(1986)-260241.

The development stopping agents employable in the light-sensitivematerial are compounds that neutralize a base or react with a base toreduce the base concentration in the layer to thereby stop development,or compounds that mutually react with silver or a silver salt tosuppress development. More specifically, examples of the developmentstopping agents include acid precursors capable of releasing acids uponheating electrophilic compounds capable of undergoing substitutionreaction with a coexisting base upon heating, nitrogen-containingheterocyclic compounds, mercapto compounds, and the like. Examples ofthe acid precursors include oxide esters described in Japanese PatentProvisional Publication Nos. 60(1985)-108837 and 60(1985)-192939 andcompounds which release acids through Lossen rearrangement described inJapanese Patent Provisional Publication No. 60-(1985)-230133. Examplesof the electrophilic compounds which induce substitution reaction withbases upon heating are described in Japanese Patent ProvisionalPublication No. 60(1985)-230134.

The antismudging agents employable in the light-sensitive materialpreferably are particles which are solid at ambient temperatures.Examples of the antismudging agents include starch particles describedin U.K. Pat. No. 1,232,347; polymer particles described in U.S. Pat. No.3,625,736; microcapsule particles containing no color former describedin U.K. Pat. No. 1,235,991; and cellulose particles, and inorganicparticles, such as particles of talc, kaolin, bentonite, agalmatolite,zinc oxide, titanium dioxide or aluminum oxide described in U.S. Pat.No. 2,711,375. Such particles preferably have a mean size of 3 to 50 μm,more preferably 5 to 40 μm. When the microcapsule is employed in thelight-sensitive material, the size of said particle is preferably largerthan that of the microcapsule.

Binders employable in the light-sensitive material preferably aretransparent or semi-transparent hydrophilic binders. Examples of thebinders include natural substances, such as gelatin, gelatinderivatives, cellulose derivatives, starch, and gum arabic; andsynthetic polymeric substances, such as water-soluble polyvinylcompounds e.g, polyvinyl alcohol, polyvinylpyrrolidone, and acrylamidepolymers. In addition to the synthetic polymeric substances, vinylcompounds dispersed in the form of latex, which are particularlyeffective to increase dimensional stability of photographic materials,can be also used. These binders can be used singly or in combination.The light-sensitive material employing a binder is described in JapanesePatent Provisional Publication No. 61(1986)-69062 (corresponding to U.S.Pat. No. 4,629,676 and European Patent Provisional Publication No.0174634A2).

A photo polymerization initiator can be contained in the light-sensitivelayer to polymerize the unpolymerized polymerizable compound after theimage-formation.

In the case that the solvent of the polymerizable compound is used, thesolvent is preferably contained in a microcapsule which is differentfrom the microcapsule containing the polymerizable compound.

Examples and usage of the other optional components which can becontained in the light-sensitive layer are also described in theabove-mentioned publications and applications concerning thelight-sensitive material, and in Research Disclosure Vol. 170, No.17029, pp. 9-15 (June 1978).

Examples of auxiliary layers which are optionally arranged on thelight-sensitive material include an image-receiving layer, a heatinglayer, an antistatic layer, an anticurl layer, a release layer, a coversheet or a protective layer, a layer containing a base or base precursorand a base barrier layer.

Instead of the use of the image-receiving material, the image-receivinglayer can be arranged on the light-sensitive material to produce thedesired image on the image-receiving layer of the light-sensitivematerial. The image-receiving layer of the light-sensitive material canbe constructed in the same manner as the layer of the image-receivingmaterial.

The light-sensitive material can be prepared, for instance, by thefollowing process.

The light-sensitive material is usually prepared by dissolving,emulsifying or dispersing each of the components of the light-sensitivelayer in an adequate medium to obtain coating solution, and then coatingthe obtained coating solution on a support.

The coating solution can be prepared by mixing liquid compositions eachcontaining a component of the light-sensitive layer. Liquid compositioncontaining two or more components may be also used in the preparation ofthe coating solution. Some components of the light-sensitive layer canbe directly added to the coating solution or the liquid composition.Further, a secondary composition can be prepared by emulsifying the oily(or aqueous) composition in an aqueous (or oily) medium to obtain thecoating solution.

The silver halide is preferably prepared in the form of a silver halideemulsion. Various processes for the preparation of the silver halideemulsion are known in the conventional technology for the preparation ofphotographic materials.

The silver halide emulsion can be prepared by the acid process, neutralprocess or ammonia process. In the stage for the preparation, a solublesilver salt and a halogen salt can be reacted in accordance with thesingle jet process, double jet process or a combination thereof. Areverse mixing method, in which grains are formed in the presence ofexcess silver ions, or a controlled double jet process, in which a pAgvalue is maintained constant, can be also employed. In order toaccelerate grain growth, the concentrations or amounts or the silversalt and halogen salt to be added or the rate of their addition can beincreased as described in Japanese Patent Provisional Publication Nos.55(1980)-142329 and 55(1980)-158124, and U.S. Pat. No. 3,650,757, etc.

The silver halide emulsion may be of a surface latent image type thatforms a latent image predominantly on the surface of silver halidegrains, or of an inner latent image type that forms a latent imagepredominantly in the interior of the grains. A direct reversal emulsioncomprising an inner latent image type emulsion and a nucleating agentmay be employed. The inner latent image type emulsion suitable for thispurpose is described in U.S. Pat. Nos. 2,592,250 and 3,761,276, JapanesePatent Publication No. 58(1983)-3534 and Japanese Patent ProvisionalPublication No. 57(1982)-136641, etc. The nucleating agent that ispreferably used in combination with the inner latent image type emulsionis described in U.S. Pat. Nos. 3,227,552, 4,245,037, 4,255,511,4,266,013 and 4,276,364, and West German Patent Provisional Publication(OLS) No. 2,635,316.

In the preparation of the silver halide emulsions, hydrophilic colloidsare advantageously used as protective colloids. Examples of usablehydrophilic colloids include proteins, e.g., gelatin, gelatinderivatives, gelatin grafted with other polymers, albumin, and casein;cellulose derivatives, e.g., hydroxyethyl cellulose, carboxymethylcellulose, cellulose sulfate, etc.; saccharide derivatives, e.g., sodiumalginate and starch derivatives; and a wide variety of synthetichydrophilic polymers, such as polyvinyl alcohol, polyvinyl alcoholpartial acetal, poly-N-vinylpyrrolidone, polyacrylic acid,polymethacrylic acid, polyacrylamide, polyvinylimidazole, andpolyvinylpyrazole, and copolymers comprising monomers constituting thesehomopolymers. Among them, gelatin is most preferred. Examples ofemployable gelatins include not only lime-processed gelatin, but alsoacid-processed gelatin and enzyme-processed gelatin. Hydrolysis productsor enzymatic decomposition products of gelatin can also be used.

In the formation of silver halide grains in the silver halide emulsion,ammonia, an organic thioether derivative as described in Japanese PatentPublication No. 47(1972)-11386 or sulfur-containing compound asdescribed in Japanese Patent Provisional Publication No. 53(1978)-144319can be used as a silver halide solvent. Further, in the grain formationor physical ripening, a cadmium salt, a zinc salt, a lead salt, athallium salt, or the like can be introduced into the reaction system.Furthermore, for the purpose of overcoming high or low intensityreciprocity law failure, a water-soluble iridium salt, e.g., iridium(III) or (IV) chloride, or ammonium hexachloroiridate, or awater-soluble rhodium salt, e.g., rhodium chloride can be used.

After the grain formation or physical ripening, soluble salts may beremoved from the resulting emulsion by a known noodle washing method ora sedimentation method. The silver halide emulsion may be used in theprimitive condition, but is usually subjected to chemical sensitization.Chemical sensitization can be carried out by the sulfur sensitization,reduction sensitization or noble metal sensitization, or a combinationthereof that are known for emulsions for the preparation of theconventional light-sensitive materials.

When the sensitizing dyes are added to the silver halide emulsion, thesensitizing dye is preferably added during the preparation of theemulsion. When the organic silver salts are introduced in thelight-sensitive microcapsule, the emulsion of the organic silver saltscan be prepared in the same manner as in the preparation of the silverhalide emulsion.

In preparation of the light-sensitive material, the polymerizablecompounds are used as the medium for preparation of the liquidcomposition containing another component of the light-sensitive layer.For example, the silver halide, including the silver halide emulsion),the reducing agent, or the leuco dye can be dissolved, emulsified ordispersed in the polymerizable compound to prepare the light-sensitivematerial. Especially, the leuco dye is preferably incorporated in thepolymerizable compound. Further, the necessary components forpreparation of a microcapsule, such as shell material can beincorporated into the polymerizable compound.

The light-sensitive composition which is the polymerizable compoundcontaining the silver halide can be prepared using the silver halideemulsion. The light-sensitive composition can be also prepared usingsilver halide powders which can be prepared by lyophilization. Theselight-sensitive composition can be obtained by stirring thepolymerizable compound and the silver halide using a homogenizer, ablender, a mixer or other conventional stirring device.

Polymers having a principal chain consisting essentially of ahydrocarbon chain substituted in part with hydrophilic groups whichcontain, in their terminal groups, --OH or nitrogen having a loneelectron-pair are preferably introduced into the polymerizable compoundprior to the preparation of the light-sensitive composition. The polymerhas a function of dispersing silver halide or other component in thepolymerizable compound very uniformly as well as a function of keepingthus dispered state. Further, the polymer has another function ofgathering silver halide along the interface between the polymerizablecompound (i.e., light-sensitive composition) and the aqueous medium inpreparation of the microcapsule. Therefore, using this polymer, silverhalide can be easily introduced into the shell material of themicrocapsule.

The light-sensitive composition can be also prepared by dispersingmicrocapsule containing silver halide emulsion as a core structure inthe polymerizable compound instead of employing the above polymer.

The polymerizable compound (including the light-sensitive composition)are preferably emulsified in an aqueous medium to prepare the coatingsolution. The necessary components for preparation of the microcapsule,such as shell material can be incorporated into the emulsion. Further,other components such as the reducing agent can be added to theemulsion.

The emulsion of the polymerizable compound can be processed for formingshell of the microcapsule. Examples of the process for the preparationof the microcapsules include a process utilizing coacervation ofhydrophilic wall-forming materials as described in U.S. Pat. Nos.2,800,457 and 2,800,458; and interfacial polymerization process asdescribed in U.S. Pat. No. 3,287,154, U.K. Pat. No. 990,443 and JapanesePatent Publication Nos. 38(1963)-19574, 42(1967)-446 and 42(1967)-771; aprocess utilizing precipitation of polymers as described in U.S. Pat.Nos. 3,418,250 and 3,660,304; a process of using isocyanate-polyol wallmaterials as described in U.S. Pat. No. 3,796,669; a process of usingisocyanate wall materials as described in U.S. Pat. No. 3,914,511; aprocess of using urea-formaldehyde or urea-formaldehyde-resorcinolwall-forming materials as described in U.S. Pat. Nos. 4,001,140,4,087,376 and 4,089,802; a process of using melamine-formaldehyde resinshydroxypropyl cellulose or like wall-forming materials as described inU.S. Pat. No. 4,025,455; an in situ process utilizing polymerization ofmonomers as described in U.K. Pat. No. 867,797 and U.S. Pat. No.4,001,140; and electrolytic dispersion and cooling process as describedin U.K. Pat. Nos. 952,807 and 965,074; a spray-drying process asdescribed in U.S. Pat. No. 3,111,407 and U.K. Pat. No. 930,422; and thelike. It is preferable, though not limitative, that the microcapsule isprepared by emulsifying core materials containing the polymerizablecompound and forming a polymeric membrane (i.e., shell) over the corematerials.

When the emulsion of the polymerizable compound (including thedispersion of the microcapsule) has been prepared by using thelight-sensitive composition, the emulsion can be used as the coatingsolution of the light-sensitive material. The coating solution can bealso prepared by mixing the emulsion of the polymerizable compound andthe silver halide emulsion. The other components can be added to thecoating solution in a similar manner as the emulsion of thepolymerizable compound.

A light-sensitive material of the invention can be prepared by coatingand drying the above-prepared coating solution on a support in theconventional manner.

The image-forming method employing the light-sensitive material of theinvention is described below.

In the use of the light-sensitive material of the invention, adevelopment process is conducted simultaneously with or after animagewise exposure.

Various exposure means can be employed in the imagewise exposure, and ingeneral, the latent image on the silver halide is obtained by imagewiseexposure to radiation including visible light. The type of light sourceand exposure can be selected depending on the light-sensitivewavelengths determined by spectral sensitization or sensitivity ofsilver halide. Original image can be either monochromatic image or colorimage.

Development of the light-sensitive material can be conductedsimultaneously with or after the imagewise exposure. The development canbe conducted using a developing solution in the same manner as the imageforming method described in Japanese Patent Publication No.45(1970)-11149. The image forming method described in Japanese PatentProvisional Publication No. 61(1986)-69062 which employs a heatdevelopment process has an advantage of simple procedures and shortprocessing time because of the dry process. Thus, the latter method ispreferred as the development process of the light-sensitive material.

Heating in the heat development process can be conducted in variousknown manners. The heating layer which is arranged on thelight-sensitive material can be used as the heating means in the samemanner as the light-sensitive material described in Japanese PatentProvisional Publication No. 61(1986)-294434. Further, thelight-sensitive material can be heated while suppressing supply ofoxygen into the light-sensitive layer from outside. Heating temperaturesfor the development process usually ranges from 80° C. to 200° C., andpreferably from 100° C. to 160° C. Various heating patterns areapplicable. The heating time is usually not shorter than 1 second,preferably from 1 second to 5 minutes, and more preferably from 1 secondto 1 minute.

During the above development process, a polymerizable compound withinthe area where a latent image of the silver halide has been formed orwithin the area where a latent image of the silver halide has not beenformed is polymerized. In a general system, the polymerizable compoundwithin the area where the latent image has been formed is polymerized.If a nature or amount of the reducing agent is controlled, thepolymerizable compound within the area where the latent image has notbeen formed can be polymerized.

In the above development process, the leuco dyes can be fixed on thesupport by the polymerization.

Where the leuco dyes and the polymerizable compound are contained in amicrocapsule, and the acid color developer is arranged outside of themicrocapsule in the light-sensitive layer, a color image (yellow) can beformed on the light-sensitive material of the invention by pressing thematerial after the development process.

The image is preferably formed on the image-receiving material. Theimage-receiving material is described hereinbelow. The image formingmethod employing the image-receiving material or the image-receivinglayer is described in Japanese Patent Provisional Publication No.61(1986)-278849.

Examples of the material employable as the support of theimage-receiving material include baryta paper in addition to variousexamples which can be employed as the support of the above mentionedlight-sensitive material. In the case that a porous material, such aspaper is employed as the support of the image-receiving material, theporous support preferably has such a surface characteristic that afiltered maximum waviness of not less than 4 μm is observed in not morethan 20 positions among 100 positions which are determined at random ona filtered waviness curve obtained according to JIS-B-0610. Further, atransparent material can be employed as the support of theimage-receiving material to obtain a transparent or a projected image.

The image-receiving material is usually prepared by providing theimage-receiving layer on the support. In the case that thelight-sensitive layer contains the acid color developer to develop theleuco dyes previous to or simultaneously with the transfarence of theleuco dyes to the image-receiving material, the image-receiving materialbe composed of a simple support.

The image-receiving layer can contain the acid color developer accordingto the color formation system of the above mentioned leuco dyes. Asmentioned above, the acid color developer is preferably contained in theimage-receiving layer.

The image-receiving layer preferably contains a polymer as binder. Thebinder which may be employed in the above-mentioned light-receivinglayer is also employable in the image-receiving layer. Further, apolymer having a transmission coefficient of oxygen of not more than1.0×10⁻¹¹ cm³ ·cm/cm² ·sec·cmHg can be used as the binder to protect thecolor of the image formed on the image-receiving material.

The image-receiving layer can contain a granulated thermoplasticcompound to obtain a glossy image. Further, the image-receiving layercan contain a white pigment (e.g., titanium dioxide) to function as awhite reflection layer. Furthermore, a photo polymerization initiator ora thermalpolymerization initiator can be contained in theimage-receiving layer to polymerize the unpolymerized polymerizablecompound.

The image-receiving layer can be composed of two or more layersaccording to the above-mentioned functions. The thickness of theimage-receiving layer preferably ranges from 1 to 100 μm, morepreferably from 1 to 20 μm.

A protective layer can be provided on the surface of the image-receivinglayer.

After the development process, pressing the light-sensitive material ofthe invention on the the image-receiving material to transfer theunfixed leuco dyes to the image-receiving material, a color image can beproduced in the image-receiving material. The process for pressing canbe carried out in various known manners.

As mentioned above, the reaction of the leuco dyes with the acid colordeveloper can be accelerated by heating. Therefore, the image-receivingmaterial is preferably heated after the transference of the leuco dyesto the image-receiving material.

This process for heating the image-receiving material after thetransference has another advantage of polymerizing the unpolymerizedpolymerizable compound which has been transferred with the leuco dyes toimprove preservability of the obtained image.

The light-sensitive material can be used for monochromatic or colorphotography, printing, radiography, diagnosis (e.g., CRT photography ofdiagnostic device using supersonic wave), copy (e.g., computer-graphichard copy), etc.

The present invention is further described by the following exampleswithout limiting the invention thereto.

EXAMPLE 1 Preparation of silver halide emulsion

In 1,000 ml of water were dissolved 20 g of gelatin and 3 g of sodiumchloride, and the resulting gelatin solution was kept at 75° C. To thegelatin solution, 600 ml of an aqueous solution containing 21 g ofsodium chloride and 56 g of potassium bromide and 600 ml of an aqueoussolution containing 0.59 mole of silver nitrate were addedsimultaneously at the same feed rate over a period of 40 minutes toobtain a silver chlorobromide emulsion having cubic grains, uniformgrain size distribution, a mean grain size of 0.35 μm and a bromidecontent of 80 mole %.

The emulsion was washed for desalting and then subjected to chemicalsensitization with 5 mg of sodium thiosulfate and 20 mg of4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene at 60° C. The yield of theemulsion was 600 g.

Preparation of silver benzotriazole emulsion

In 3,000 ml of water were dissolved 28 g of gelatin and 13.2 g ofbenzotriazole, and the solution was kept at 40° C. while stirring. Tothe solution was added 100 ml of an aqueous solution of 17 g of silvernitrate over 2 minutes. Excessive salts were sedimented and removed fromthe resulting emulsion by pH-adjustment. Thereafter, the emulsion wasadjusted to pH 6.30 to obtain a silver benzotriazole emulsion. The yieldof the emulsion was 400 g.

Preparation of light-sensitive composition

In 100 g of trimethylolpropane triacrylate were dissolved 0.40 g of thefollowing copolymer, 5.6 g of the following leuco dye (1) and 2 g ofEmulex NP-8 (tradename of Nippon Emulsion Co., Ltd.). ##STR10##

To 18.00 g of the resulting solution were added a solution in which 0.16g of the following reducing agent (I) and 1.22 g of the followingreducing agent (II) are dissolved in 1.80 g of methylene chloride.##STR11##

To the mixture were further added 3.50 g of the silver halide emulsionand 3.35 g of the silver benzotriazole emulsion, and the mixture wasstirred at 15,000 r.p.m. for 5 minutes to obtain a light-sensitivecomposition.

Preparation of light-sensitive microcapsule

To 10.51 g of 18.6% aqueous solution of Isobam (tradename of KurarayCo., Ltd.) was added 48.56 g of 2.89% aqueous solution of pectin. Afterthe solution was adjusted to a pH of 4.0 using 10% sulfuric acid, thelight-sensitive composition was added to the resulting solution, and themixture was stirred at 7,000 r.p.m. for 2 min. to emulsify thelight-sensitive composition in the aqueous medium.

To 72.5 g of the aqueous emulsion were added 8.32 g of 40% aqueoussolution of urea, 2.82 g of 11.3% aqueous solution of resorcinol, 8.56 gof 37% aqueous solution of formaldehyde, and 2.74 g of 8.76% aqueoussolution of ammonium sulfate in this order, and the mixture was heatedat 60° C. for 2 hours while stirring. After the mixture was adjusted toa pH of 7.0 using 10% aqueous solution of sodium hydroxide, 3.62 g of30.9% aqueous solution of sodium hydrogen sulfite was added to themixture to obtain a dispersion containing light-sensitive microcapsules.

Preparation of light-sensitive material

To 10.0 g of the light-sensitive microcapsule dispersion were added 1.0g of 1% aqueous solution of the following anionic surfactant, 1.0 g of10% solution (solvent: water/ethanol=50/50 as volume ratio) of guanidinetrichroloacetate to prepare a coating solution. ##STR12##

The coating solution was uniformly coated on a polyethyleneterephthalatefilm (thickness: 100 μm) using a coating rod of #40 to give a layerhaving a wet thickness of 70 μm and dried at about 40° C. to obtain alight-sensitive material (A).

EXAMPLE 2

Each of the light-sensitive materials (B) to (D) was prepared in thesame manner as in Example 1 except that each of the following leuco dyes(3), (11) and (13) (each of the amount is set forth in Table 1) wasrespectively used in place of 5.6 g of the leuco dye (1). ##STR13##

COMPARISON EXAMPLE 1

Each of the light-sensitive materials (E) and (F) was prepared in thesame manner as in Example 1 except that each of the following leuco dyes(a) and (b) (each of the amount is set forth in Table 1) wasrespectively used in place of 5.6 g of the leuco dye (1). ##STR14##

Preparation of image-receiving material

To 125 g of water was added 11 g of 40% aqueous solution of sodiumhexametaphosphate, and were further added 34 g of zinc3,5-di-α-methylbenzylsalicylate and 82 g of 55% slurry of calciumcarbonate, followed by coarsely dispersing in a mixer.

The coarse dispersion was then finely dispersed in Dynomill dispersingdevice. To 200 g of the resulting dispersion were added 6 g of 50% latexof SBR (styrene-butadiene rubber) and 55 g of 8% aqueous solution ofpolyvinyl alcohol, and the resulting mixture was made uniform. Themixture was then uniformly coated on an art paper having a basis weightof 43 g/m² to give a layer having a wet thickness of 30 μm and dried toobtain an image-receiving material.

Evaluation of light-sensitive material

Each of the light-sensitive materials (A) to (F) prepared in Examples 1& 2 and Comparison Example 1 was imagewise exposed to light using atungsten lamp at 200 lux for 1 second and then heated on a hot plate at125° C. for 30 seconds. Each of the exposed and heated light-sensitivematerials was then combined with the image-receiving material and passedthrough press rolls under pressure of 350 kg/cm². The density of thepositive color image (yellow color image) obtained on theimage-receiving material was measured using a reflection densitometer(measured wavelength: 440 nm).

The results are set forth in Table 1.

                  TABLE 1                                                         ______________________________________                                        Light-                                                                        Sensitive                                                                              Leuco   Amount     Maximum Minimum                                   Material Dye     (g)        Density Density                                   ______________________________________                                        (A)       (1)    5.6        1.36    0.12                                      (B)       (3)    5.6        1.36    0.11                                      (C)      (11)    5.4        1.35    0.12                                      (D)      (13)    5.5        1.35    0.11                                      (E)      (a)     5.4        1.05    0.12                                      (F)      (b)     5.0        0.82    0.15                                      ______________________________________                                    

It is apparent from the results in Table 1 that each of thelight-sensitive materials (A) to (D) according to the invention forms animproved positive image which has a high maximum density and a lowminimum density compared with the light-sensitive materials (E) and (F)containing a known leuco dye. Further, it has been observed that each ofthe light-sensitive materials of the invention forms an image havingsatisfactory durability to exposure to light.

We claim:
 1. A light-sensitive material comprising a light-sensitivelayer containing silver halide, a reducing agent, an ethylenicunsaturated polymerizable compound and a leuco dye provided on asupport, wherein the leuco dye is a compound having the followingformula (II): ##STR15## in which R¹ and R² are the same groups selectedfrom the group consisting of an alkyl group and a cycloalkyl group; R³and R⁴ are the same groups selected from the group consisting of analkyl group, a cycloalkyl group and an alkoxy group; and the sum ofcarbon atoms contained in the groups of R¹ and R³ is not less than
 5. 2.The light-sensitive material as claimed in claim 1, wherein the leucodye is dissolved in the polymerizable compound.
 3. The light-sensitivematerial as claimed in claim 1, wherein the polymerizable compound andthe leuco dye are contained in microcapsules which are dispersed in thelight-sensitive layer, said leuco dye being dissolved in thepolymerizable compound.
 4. The light-sensitive material as claimed inclaim 1, wherein the silver halide, the polymerizable compound and theleuco dye are contained in microcapsules which are dispersed in thelight-sensitive layer, said leuco dye being dissolved in thepolymerizable compound.
 5. The light-sensitive material as claimed inclaim 1, wherein the reducing agent, the polymerizable compound and theleuco dye are contained in microcapsules which are dispersed in thelight-sensitive layer, said leuco dye being dissolved in thepolymerizable compound.
 6. The light-sensitive material as claimed inclaim 1, wherein the leuco dye is contained in an amount of from 0.5 to50 weight % based on the amount of the polymerizable compound in thelight-sensitive layer.